1. Technical Field
The present invention relates to a method for preparing an ion source from nanoparticles. More particularly, the present invention relates to a method for preparing an ion source from nanoparticles, applicable to the technology of ion source preparation.
2. Description of Related Art
Ion implantation technology has been broadly used to dope semiconductor with ions. In a nutshell, the ion implantation technology involves implanting ions with certain energy into a substrate so as to alter the characteristics of the substrate.
FIG. 4 depicts the structure of a known ion implanter 200. As shown in FIG. 4, the ion implanter 200, which is configured for performing ion implantation, mainly includes an ion source system 100, an analyzing magnetic field 230, an ion acceleration system 240, and a target chamber 250. The ion source system 100 is a system for generating ions, in which an ion source material is ionized to form positively or negatively charged ions. Then, the ions are extracted by an extraction electrode 210. After the analyzing magnetic field 230 selects the needed ions, the selected ions form an ion beam 220 to enter the ion acceleration system 240. The ions are accelerated by an electric field in the ion acceleration system 240 before entering the target chamber 250, where the ions are implanted into a substrate to alter the characteristics thereof.
The ion source system 100 provides an ion source. More specifically, the ion source system 100 is equipped with a stainless tube. The heated stainless tube can melt solid lumps and vaporize the solid lumps into a gaseous state, such that the resultant gas enters an arc chamber by diffusion. In the arc chamber, the gas collides with thermal electrons emitted by a filament and is thereby ionized so as to form the ion source. To enhance the efficiency of ionization, magnets are disposed outside the arc chamber to form a magnetic field, thus enabling electronic gyration in the arc chamber and hence increasing the probability of collision.
Originally, trivalent atoms (e.g., boron atoms) or pentavalent atoms (e.g., phosphorus and arsenic atoms) were used as the ion source material; however, metal materials are now also being used. A metallic ion source material such as gold, copper, and cobalt is generally in the form of solid lumps. However, due to their high melting points (e.g., over 900° C.), metal materials cannot generate sufficiently high vapor pressure under low temperature (e.g., 10° C. to 800° C.). Therefore, it is difficult to apply metallic ion source materials to high-dose doping processes. Furthermore, commercially available ion implanters are designed for doping with trivalent or pentavalent atoms. As a result, some metal materials provided in these known ion implanters cannot be heated over 1000° C., thus hindering the application of ion implantation technology.